## Copyright (C) 2003 David Bateman
##
## This program is free software; you can redistribute it and/or modify
## it under the terms of the GNU General Public License as published by
## the Free Software Foundation; either version 2 of the License, or
## (at your option) any later version.
##
## This program is distributed in the hope that it will be useful,
## but WITHOUT ANY WARRANTY; without even the implied warranty of
## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
## GNU General Public License for more details.
##
## You should have received a copy of the GNU General Public License
## along with this program; If not, see <http://www.gnu.org/licenses/>.

## -*- texinfo -*-
## @deftypefn {Function File} {@var{d} = } dftmtx (@var{n})
##
## If @var{n} is a scalar, produces a @var{n}-by-@var{n} matrix @var{d}
## such that the Fourier transform of a column vector of length @var{n}
## is given by @code{dftmtx(@var{n}) * x} and the inverse Fourier transform
## is given by @code{inv(dftmtx(@var{n})) * x}. In general this is less
## efficient than calling the @dfn{fft} and @dfn{ifft} directly.
## @end deftypefn

function d = dftmtx(n)

  if (nargin != 1)
    error ("usage: d = dftmtx (n)");
  endif

  if (!isscalar(n))
    error ("dftmtx: argument must be scalar");
  endif
    
  d = fft(eye(n));

endfunction
